test-lib-functions: remove test_subcommand_inexact

The implementation of test_subcommand_inexact() was originally introduced in e4d0c11c0 (repack: respect kept objects with '--write-midx -b', 2021-12-20) with the intention to allow finding a subcommand based on an initial set of arguments. The inexactness was intended as a way to allow flexible options beyond that initial set, as opposed to test_subcommand() which requires that the full list of options is provided in its entirety. The implementation began by copying test_subcommand() and replaced the repeated argument 'printf' statement to append ".*" instead of "," to each argument. This caused it to be more flexible than initially intended. The previous change deleted the only use of test_subcommand_inexact, so instead of editing the helper, delete it. Helped-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>